The present invention relates in general to an information multiplex transmission system for facilitating information transmission between terminal units or work stations and, in more particular, to a broad band network system for causing two arbitrary terminal units among the terminal units to transmit various data signal such as speech data, coded computer data and video data therebetween.
Utilization of various work stations such as business-use personal computers, facsimile (FAX) units, telephone signal units and the like in offices is increasing to improve office efficiency. Along with this tendency, the data signal transfer system for causing the terminals or work stations to transmit signals therebetween has become increasingly important to the effective exchange of signals between work stations.
Different work stations generate signals in different forms. For example, telephones exchange speech data in accordance with analog speech signals. However, personal computers as terminal units process coded digital data. Signals such as computer digital signals having a different form from that of analog speech signals cannot be transmitted per se onto telephone lines on which analog signals are transmitted. Therefore, conventionally, special signal transfer lines are added to transmit signals having a special form. Recently, a so-called "broad band network system" has been proposed wherein a broad band signal transmission network such as a coaxial cable or optical fiber cable is commonly installed between different types of work stations, and the frequency bandwidth of the network is divided into frequency ranges each of which is alotted to the transmission of data signals in a specific form. However, at present, in order to perform data communication between two arbitrary work stations among a number of work stations, a wide frequency band having a predetermined level or higher is required as a band for guaranteeing transmission of a signal having a specific form. Therefore, the signal transmission efficiency of the broad band network system is degraded, and the number of stations which may be connected to a single broad band network system is limited.